What Is Breitbart News?

The Republican presidential nominee, Donald J. Trump, has hired a top executive from Breitbart News, Stephen Bannon, as his campaign’s chief executive, raising expectations that Mr. Trump will adopt the more aggressive style that the site has championed.

So, What Is Breitbart?

The Breitbart News Network, usually just called Breitbart, is a conservative-leaning news website.

The site that bears his name comprises about a dozen different verticals that feature original reporting and commentary, including three of its most prominent sites: Big Government, Big Journalism and Big Hollywood. A fourth “Big” site, BigPeace.com, now redirects to Breitbart’s National Security section.

According to SimilarWeb, a web analytics platform, Breitbart’s traffic is comparable to that of Slate and Gawker, and it has received more visitors than either of those two sites over the past several months.

Who Was Andrew Breitbart?

As a blogger in the early 2000s, Mr. Breitbart was taken under the wing of Matt Drudge before setting out on his own. In a column after Mr. Breitbart’s death, titled “The Provocateur,” David Carr of The New York Times wrote that he “understood in a fundamental way how discourse could be profoundly shaped by the pixels generated far outside the mainstream media he held in such low regard.”

Ben Shapiro, a conservative commentator who was 17 when he met Mr. Breitbart and who became the editor-at-large of Breitbart.com in 2012 about three weeks before Mr. Breitbart died, said in an interview Wednesday that Mr. Breitbart was not ideologically driven.

“Andrew’s whole animating focus was ‘I don’t like bullies in the political sphere and I’ll fight the bullies,’ ” he said.

Not all of Mr. Breitbart’s friends are happy with the direction in which Mr. Bannon took the site. “As I said when I left Breitbart,” Mr. Shapiro said, “I am absolutely appalled by what Breitbart’s become. I think Bannon has perverted Breitbart’s legacy.”

What Are the Site’s Claims to Fame?

Under the supervision of its founder, Breitbart gained prominence by breaking news about a series of scandals involving liberal politicians, bureaucrats and organizations, and by relentlessly pushing those stories. Is the site divisive? As a Breitbart favorite, Sarah Palin, might put it: You betcha!

The website is loathed by many liberals, moderates and establishment Republicans who say it stokes a partisan atmosphere and misleads readers in order to escalate what they see as nonissues.

What Happened With Acorn?

In 2009, on his site Big Government, Mr. Breitbart released videos of workers for the Association of Community Organizations for Reform Now (better known as Acorn) that appeared to show employees of the community organization advising clients on criminal activities. The videos, filmed by conservative activists, led contributions to Acorn to plummet, and the organization announced in 2010 that it was closing all its offices.

Liberal media watchdog groups, including FAIR, criticized the mainstream media, including The Times, for much of its reporting on the story. The Times’s public editor at the time, Clark Hoyt, wrote about how conservatives and liberals viewed the story differently, exemplifying the effect that outlets like Breitbart had on the public conversation.

Twitter Bans @Nero

A technology editor at Breitbart, Milo Yiannopoulos, is one of the more well-known and provocative employees of the site. Last month, he was banned from Twitter, where he tweeted as @nero. Mr. Yiannopoulos was accused of helping to instigate a campaign of sexist and racist abuse against the actress and “Saturday Night Live” comic Leslie Jones.

Support for the Trump Campaign

During the 2016 presidential campaign, including the Republican primaries, the site has offered exceedingly favorable coverage to the campaign of Donald J. Trump, often to the dismay of mainstream conservatives and the Republican Party establishment.

A Reporter’s Assault Claim

The site drew widespread attention in March, when Michelle Fields, a reporter for Breitbart News, accused Corey Lewandowski, then the campaign manager for Mr. Trump, of assaulting her after a news conference in Jupiter, Fla.

The incident caused an uproar within Breitbart, as several staff members, including Mr. Shapiro, left the organization, outraged that Mr. Bannon and the site did not support Ms. Fields. Instead, it appeared to be defending the campaign and Mr. Lewandowski.

“I said at the time that Bannon had used Breitbart as basically a steppingstone for him to get in close with the Trump campaign,” Mr. Shapiro said.